Chinese scientists discover way to turn homosexuality on and off in male mice

A lack of serotonin leads male mice to lose sexual interest in females, say a group of Chinese scientists.

Big news from the world of science today: A group of Chinese scientists from the National Institute of Biological Sciences have appeared to find a way to regulate sexual preference in male mice.The secret apparently lies in the brain chemical serotonin — male mice bred without this chemical lose their sexual interest in females.These findings have been published in the international weekly science journal, Nature, and is understood to be the first time that a neurotransmitter has been shown to play a role in the sexual preference of a mammal.LiveScience.com translates the research by neuroscientist Yi Rao and his collaborators into simple layman terms:

Rao and his team genetically engineered male mice to lack either serotonin-producing neurons or a protein that is crucial for making serotonin in the brain. Both types of altered mouse couldn’t make serotonin.Unlike typical males, mice deficient in the neurotransmitter showed no inclination to mount sexually receptive females more than males, nor did they prefer to smell females’ genital odors or bedding. Instead, they climbed onto males and serenaded them with ultrasonic love songs more frequently than normal. Males emit these vocalizations when they encounter females to make them more receptive to mating.While all of the males who possessed serotonin mounted females first, nearly half of the mice that lacked serotonin clambered onto males before females, and about 60 percent spent more time sniffing or hovering over the genital odors and bedding from males than from females.When the researchers injected a compound into these mice to restore neurotransmitter levels, they found that the animals mounted females more than males. But too much serotonin reduced male-female mounting, suggesting that the amount of this chemical must stay within a certain range to foster heterosexual rather than homosexual behaviors.

Does serotonin play a similar role in the sexual orientation of other mammals, and in particular, humans? Researchers are quick to warn us not to read too much into the results.

Said Professor Keith Kendrick, a neuroscientist at the Babraham Institute in Cambridge, to the BBC: “In terms of having potential relevance to understanding human sexual preference/orientation, we are of course far less influenced by odour cues in this context than mice are. There is some very limited evidence for altered responses to selective serotonin uptake inhibitors (SSRIs) in the brains of homosexuals, but we have been using psychoactive drugs which either increase or decrease serotonin function for quite some time now, and while effects on sexual arousal, impulsivity and aggression have often been reported, no effects on sexual preference/orientation have. At this time therefore any potential links between serotonin and human sexual preferences must be considered somewhat tenuous.”While the results of this research has gained widespread interest in the international media, mainstream Chinese media appear to be relatively uninterested for now. So far, the only mainland Chinese publication to have reported the finding is the Shanghai-based Wenhui Daily 《文汇报》.